It has been reported that urinary stents and catheters have been used by ancient Egyptians in the form of papyrus and lead catheters (Contemporary Urology, October 2004, p. 16). Ureteral stents are a common tool in urologic practice. Since the development of the double-pigtail stent by Finney about three decades ago [J. Urol., 120 (6), 578 (1978)], the search for the ideal stent continues; and patients continue to suffer from stent-related morbidity ranging from irritation and discomfort to sepsis and renal compromise from encrusted “forgotten” stents. During the search for the ideal endoureteral stent (E-stent) and related endo-urological devices, inventors and investigators of the prior art tried to exploit advances made in biomaterials, particularly absorbable or transient ones.
A typical illustration of the prior efforts is provided in U.S. Pat. No. 6,733,536 dealing with a urethral stent device. In this disclosure, a stent for treatment of a body lumen through which a flow is effected on either side of a sphincter was described, the stent comprising one or more windings and having an inner core substantially covered by an outer core and including a first segment, a second segment, and a connecting member disposed between the segments. When the stent is positioned within a patient's urinary system, the first segment and second segments are located on either side of the external sphincter to inhibit migration of the stent while not interfering with the normal functioning of the sphincter. The outer coating comprises an absorbable material that provides temporary structural support to the stent. After absorption of substantially all the outer coating of the stent, the remaining relatively compliant inner core facilitates easy removal by the patient by pulling a portion of the stent that extends outside the patient's body for this purpose.
In a review by Beiko and coworkers [J. Urology, 171, 2438 (2004)], it was noted that (1) the ideal substance for urinary tract biomaterial should incorporate certain features, such as biological inertness, chemical stability in urine, resistance to infection and encrustation, excellent long-term urinary flow, stability following placement, and no significant discomfort to the patient; and (2) urethral stents made of self-reinforced 80/20 l-lactide/glycolide copolymer were inserted in situ via cystoscopy into rabbit prostatic urethra and was found to be soft and almost completely degraded at three months—the material did not encroach into the urethral wall and there was no encrustation.
U.S. Pat. No. 6,585,773 describes an insertable stent for joining together and facilitating healing of adjacent tissues as in the case of sutureless end-to-end urethral and heterograft anastomosis. U.S. Pat. No. 6,685,734 describes a device for inserting a stent in a body cavity, particularly useful for inserting a stent into a human male urethra to treat prostatic hyperplasia, whereby such device has an elongated member for removably receiving a stent and means capable of protruding from the member to either locate an obstruction, such as the sphincter muscle, in the body cavity or to prevent the stent from sliding off of the member, or both. And U.S. Pat. No. 6,524,345 describes a suitable composition for constructing the stent described in U.S. Pat. No. 6,685,734. That composition comprises a biodegradable polymer interdispersed with ceramic particulates that are visible by radioscopy.
However, none of the prior art described a combination of absorbable endo-urological stent and non-absorbable applicator combination that permit facile insertion and secured location/maintenance of the stent at the intended site, wherein the insertion is associated with predictable change in stent configuration and dimensions to insure secure immobilization, prevent migration, maintain uninterrupted functionality over a predetermined period of time, and eventual safe, regulated disintegration and absorption. This provided an incentive for the present inventor to explore the use of contemporary absorbable biomaterials for the production of a novel endo-urological stent in copending U.S. patent application Ser. No. 60/600,336. The present invention extends to specific new designs of patient-customized, non-migrating, fiber-reinforced, absorbable/disintegratable endoureteral composite stents that are useful in maintaining optimum ureteral patency, for a predetermined period of time, while being securely placed in the ureteral tract.